With the increase in mobile devices and the prevalence of wireless networking, wireless display capability is experiencing rapid growth. In wireless display technology, a wireless link between a source device and sink display device replaces the typical data cable between computer and monitor. Wireless display protocols are typically peer-to-peer or “direct” and most usage models have a mobile device transmitting media content to be received and displayed by one or more external monitors. In a typical screencasting application for example, a smartphone may be wirelessly coupled to one or more external monitors, display panels, televisions, projectors, etc.
Wireless display specifications (e.g., WiDi v3.5 by Intel Corporation, and Wi-Fi Display v1.0 or WFD from the Miracast program of the Wi-Fi Alliance) have been developed for the transmission of compressed video data and audio data streams over wireless local area networks of sufficient bandwidth. For example, current wireless display technologies utilizing WiFi technology (e.g., 2.4 GHz and 5 GHz radio bands) are capable of streaming encoded full HD video data as well as high fidelity audio data (e.g., 5.1 surround).
For both wireless and wired transmission of media content, the timing of the rendered video signal may deviate from the timing of the rendered audio signal as the video and audio data are decoded and rendered by a receiving display (sink) device. This timing difference or mismatch is commonly known as “lip sync” error, because the error is most readily apparent to the wireless display user when the content represents a person speaking. Lip sync error may be quantified as amount of time audio departs from perfect synchronization with the video where a positive time number indicates the audio leads the video and a negative number indicates the audio lags the video. Lip sync error may vary over time, occurring for example when an A/V stream is corrupted during transmission. Lip sync error of between 50 millisecond and a few seconds are not uncommon.
Certain wired media content receivers, for example complying with a High Definition Media Interface (HDMI) standard (e.g., 2.0 released on Sep. 4, 2013), include a Lip Sync function by which audio processing time may be adjusted automatically to remove errors in audio/video timing. To date however, wireless display technology lacks the capability to sufficiently address lip sync issues.